1. Field of the Invention
The present invention relates to a bonding apparatus and more particularly to a bonding apparatus which is suitable for use in bonding a workpiece that has a large bonding area.
2. Prior Art
Wire bonding apparatuses that performs bump formation or wire connections, etc. are generally divided into the two main types.
The first main type is a vertically driven type. In this vertically driven type, a slider is disposed on a linear guide that has a vertical guide so that the slider can move upward and downward, an ultrasonic horn that has a capillary is attached to a horn holder, and the horn holder is attached to the slider.
An example of such a vertically driven type apparatus is described in Japanese Patent No. 3220483 (Laid-Open No. H05-74838).
The second main type is a supporting-point swinging type. In this supporting-point swinging type, an ultrasonic horn which has a capillary is attached to a horn holder. The horn holder is caused to swing about the supporting point of a cruciform plate spring that supports the horn holder, or the horn holder is fastened to a supporting shaft which is rotatably supported so that the horn holder is caused to swing about this supporting shaft.
Examples of such a supporting-point swinging type apparatus are described in Japanese Patent No. 2814154 (Laid-Open No. H04-317343), Japanese Patent No. 2860650 (Laid-Open No. H10-74785), etc.
In the vertically driven type, the length of the linear guide must be sufficient enough so that the capillary contacts the workpiece, and the linear guide is extended downward from the horizontal plane of the bonding surface of the workpiece. Accordingly, the workpiece is limited to a size that does not contact the linear guide. Furthermore, since such components as the ultrasonic horn, horn holder, slider, etc. which are heavy are caused to move upward and downward, the inertia is large when these elements are driven at a high speed, and bonding of small balls is especially difficult.
In the supporting-point swinging type, when the capillary is in contact with a workpiece, the capillary must be perpendicular to the workpiece. Accordingly, the supporting point or supporting shaft that constitutes the center of rotation of the horn holder is set to be at the same height as the tip end of the capillary. Consequently, the horn holder and the supporting point or supporting shaft are positioned on a horizontal plane of the bonding surface of the workpiece, so that the size of the workpiece is, like in the above-described vertically driven type, limited. Furthermore, since the capillary swings about the supporting point or supporting shaft, a correction in the forward-rearward direction (the axial direction of the ultrasonic horn) is necessary in order to raise and lower the capillary more or less perpendicularly.